I use any pen with pigma ink. It is permanent. I use the gelly roll pens, from the scrapbook aisle, a lot and haven't had any issues. I do not use the glitter ones or the ones that go on in one color and you "erase" it and a second color appears. I also use any fabric marker. I do not use the Sharpie markers as they bleed too easily. Again, I heat set everything first before washing.